The present invention relates generally to door lock mechanisms and particularly to a lock mechanism for use on doors where automatic unlocking is a requirement or at least highly desirable. Locks on so called panic doors at emergency exits fall within this category. Municipal ordinances and/or state regulations ordinarily require automatic unlocking of panic doors to enable unhindered egress from a building.
Panic doors installed within public buildings, in accordance with the applicable building code, must permit opening without special knowledge being required of the person for obvious reasons. As a practical matter, such doors must be securely locked when not in use to prevent unauthorized entry into a building. For one reason or another panic doors often serve as a means for unauthorized entry particularly in apartment houses and public buildings where the panic doors exit into alleys, little used walkways and the like. Commonly found on panic doors is a lock mechanism including an actuating pressure bar offset inwardly and extending across the door which unlocks the door upon a person pushing against same. The bolt in such lock mechanisms swings about a vertical axis and is susceptible to tampering. A further drawback is the necessity to physically test the door to determine whether or not it is locked as the condition of same is not discernible simply from door appearance. A still further disadvantage of known panic door locks is their complexity and cost.